[MITgcm-support] How to simulate the geostrophic current?

[miaocb]

  Hi Martin,
     Thanks for your quick reply.  My aim is to simulate internal tides with horizontally varying stratification. In order to sustain such a stratification, a general 
circulation should be produced. And then barotropic tides are imposed at the open boundaries for producing internal tides. There are two ways to produce the 
general circulation which have been considered by me.  The first way is to diagnose a geostrophic or quasi-geostrophic current which is consistent with the horizonally 
varying stratification. The second way is to simulate the general circulation with wind forcing, heat fluxes and volume fluxes through open boundaries. The first way seems 
simple, but I don't know whether it is applicable.  I do not need a purely gestrophic balance, I just want to get the current that is able to sustain the stratification.
    
   Thanks again.

Paul Miao

>Date: Tue, 15 Mar 2011 11:28:48 +0100
>From: Martin Losch <Martin.Losch at awi.de>
>To: mitgcm-support at mitgcm.org
>Subject: Re: [MITgcm-support] How to simulate the geostrophic current?
>Message-ID: <AB1963BE-ABA8-4C2C-BADF-8F48C52CE443 at awi.de>
>Content-Type: text/plain; CHARSET=US-ASCII

>Hi Paul,

>it's not clear to me what you want to do. The MITgcm implements the full so-called primitive equations (actually, it can also do the filtered Boussinesque Navier-Stokes equations). >The dominant balance in large scale circulation simulations with the MITgcm (but also with other GCMs) will be the geostrophic balance.
>What you are trying to do looks a bit like "diagnostic runs", where T/S are basically held fixed via restoring and the model computes some velocity field from that (as in the early papers >by Bryan and Cox?). This will not give you a purely gestrophic flow field, as more terms of the balance are involved. For purely gestrophic balance, you'll have to turn of the advection >of momentum, T,S, turn off the viscosity and diffusion. Maybe these parameters help:
>tempStepping = .false., 
>saltStepping = .false.,
>momViscosity = .false.,
>momAdvection = .false.,
>momForcing = .false.,
>and when there is no timestep in T/S, then you do not need the rbcs package, because T/S will not change.

>I have no idea if this will do what you want, but it will give you a model run with T/S fixed in time and just the geostrophic balance left after the transients have faded (du/dt is not >turned off!).

>M.